Field of the Application
The application generally relates to cell selection/reselection, and more particularly to cell selection/reselection with Application-specific Congestion control for Data Communication (ACDC).
Description of the Related Art
With growing demand for ubiquitous computing and networking, various wireless technologies have been developed, including Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA-2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, LTE-Advanced (LTE-A) technology, and Time-Division LTE (TD-LTE) technology, etc.
Using LTE technology as an example, the Application-specific Congestion control for Data Communication (ACDC) was first introduced in Release 13 of the 3rd Generation Partnership Project (3GPP) specifications. ACDC aims to provide a more flexible access control mechanism which applies based on the purpose of UE's access attempt. Basically, ACDC groups applications in categories of importance, and applies access controls to lesser categories first, sparing more important applications from denial or deferral of access until and unless the level of congestion is severe enough that they must also be affected.
However, according to release 12 of the 3GPP TS 36.304, a UE in the idle mode only takes the measured signal qualities and the priority levels of the candidate cells into account during the cell selection/reselection procedure. As a result, despite the fact that there are cells which have lower priority levels but the ACDC has not been enabled therein, the UE will choose to camp on the cell which has a higher priority level but the ACDC has been enabled therein, causing a negative user experience with only limited services available.